1.3.2 Emulsion stability
An emulsion is a thermodynamically unstable system, as it will form only if energy is applied,
and need to be kinetically stabilised in order to be stable over time (Butt et al., 2006;
McClements, 2002). An emulsion is usually prepared by high-speed homogenization, during
which the droplets continuously breaks up and recoalesce. The final droplet size is
determined by the timescale of the breakup and recoalescence processes. Coalescence is the
process where the “film” between two droplets rupture, causing them to fuse into a larger
droplet due to the Laplace pressure (Norde, 2003). If an emulsion of pure oil and water is left
to stand, coalescence between the dispersed droplets will reduce the surface area,
eventually leading to the two immiscible liquids separating into a low-density phase (oil) and
high density phase (water) as showed in Figure 1.3.1. This phenomenon is called phase
separation or demulsification, and leads to a lower Gibbs free energy of the system